A sample of radioactive element contains 4 10¹⁶ active nuclei. The half-life of the element is 10 decays, then number of decayed nuclei after 30 days is:

Step-by-step solution

Half life number is given by n= 1 T = 30 10 =3 Nuclear of active nuclei left after n half-life is aligned & N=N₀ ( 1 2 )^n = & 4 10¹⁶ (2)^3 =0.5 10¹⁶ & Decay nuclei =N₀-N = & 4 10¹⁶-0.5 10¹⁶ = & 3.5 10¹⁶ aligned